Java Reference
In-Depth Information
c)
Write a statement that opens file
"newmast.ser"
for output (and creation)—use
ObjectOutputStream
variable
outNewMaster
to wrap an
OutputStream
.
d)
Write a statement that reads a record from the file
"oldmast.ser"
. The record is an
object of class
Account
—use
ObjectInputStream
variable
inOldMaster
. Assume class
Account
is the same as the
Account
class in Fig. 15.9
e)
Write a statement that reads a record from the file
"trans.ser"
. The record is an object
of class
TransactionRecord
—use
ObjectInputStream
variable
inTransaction
.
f)
Write a statement that outputs a record of type
Account
to the file
"newmast.ser"
—use
ObjectOutputStream
variable
outNewMaster
.
Answers to Self-Review Exercises
15.1
a) False. These three streams are created for you when a Java application begins executing.
b) True. c) True. d) False. Text files are human readable in a text editor. Binary files might be hu-
man readable, but only if the bytes in the file represent ASCII characters. e) True. f) False. Class
Formatter
contains method
format
, which enables formatted data to be output to the screen or to
a file.
15.2
a)
Scanner inOldMaster =
new
Scanner(Paths.get(
"oldmast.txt"
));
b)
Scanner inTransaction =
new
Scanner(Paths.get(
"trans.txt"
));
c)
Formatter outNewMaster =
new
Formatter(
"newmast.txt"
);
d)
Account account =
new
Account();
account.setAccount(inOldMaster.nextInt());
account.setFirstName(inOldMaster.next());
account.setLastName(inOldMaster.next());
account.setBalance(inOldMaster.nextDouble());
e)
TransactionRecord transaction =
new
Transaction();
transaction.setAccount(inTransaction.nextInt());
transaction.setAmount(inTransaction.nextDouble());
f)
outNewMaster.format(
"%d %s %s %.2f%n"
,
account.getAccount(), account.getFirstName(),
account.getLastName(), account.getBalance());
15.3
a)
ObjectInputStream inOldMaster =
new
ObjectInputStream(
Files.newInputStream(Paths.get(
"oldmast.ser"
)));
b)
ObjectInputStream inTransaction =
new
ObjectInputStream(
Files.newOutputStream(Paths.get(
"trans.ser")
));
c)
ObjectOutputStream outNewMaster =
new
ObjectOutputStream(
Files.newOutputStream(Paths.get(
"newmast.ser"
)));
d)
Account = (Account) inOldMaster.readObject();
e)
transactionRecord
=
(TransactionRecord)
inTransaction.readObject();
f)
outNewMaster.writeObject(newAccount);
Exercises
15.4
(File Matching)
Self-Review Exercise 15.2 asked you to write a series of single statements.
Actually, these statements form the core of an important type of file-processing program—namely,
a file-matching program. In commercial data processing, it's common to have several files in each
application system. In an accounts receivable system, for example, there's generally a master file con-
taining detailed information about each customer, such as the customer's name, address, telephone
number, outstanding balance, credit limit, discount terms, contract arrangements and possibly a
condensed history of recent purchases and cash payments.
